Canada wildfires from space and ground – Seeing beyond the flames: a series of observations

Since July, the province of British Columbia (BC), west coast of Canada, has been impacted by massive and violent wildfires. Such events are visually impressive. They can be a constructive force by maintaining the overall health and functioning of the forest ecosystem, but also a destructive force due to devastating impacts on the local population, soil and our atmosphere: e.g. visibility reduction, air quality deterioration caused by smoke fine particles (aerosols) that are harmful for health population and on a longer term, climate.

These effects can easily be seen by different “eyes”. While BC is known for its clean, fresh air, the visibility reduction occurs as the increased concentration of smoke particles leads to more extinction of the sunlight passing through the atmosphere. This results in the formation of haze and the dark grey smoke that we see. The particles can also attract water, acting as condensation nuclei for droplet formation and a subsequent further reduction in visibility as fog and clouds form.

Although the fires themselves are fairly localized in the interior of BC, their overall impact is not, with the smoke traveling far away from the source region – up to thousands of kilometers! Atmospheric and fire emission models are used to predict the amount and trajectory of smoke according to the prevailing circulation and dispersion patterns allowing for air quality forecasts and warnings, such as the Government of Canada’s wildfire smoke prediction system: FireWork.

FireWork forecast of small particulate matters (PM2.5) concentration at the surface level from forest fire sources for 0000 UTC on 12 August, 2017. Notice the particles are carried far from their origin in central BC: to northern and central Canada; the US mid-west; and along the west coast of North America, all the way to Mexico (Source: https://weather.gc.ca/firework/).

Satellite observations are vital to monitor such disasters. Not only do they provide an overview image from the top of the atmosphere of the raging fires, which already gives spectacular maps, they also allow detection of the substances released in the air by these episodes and follow their dispersion. This is vital for predicting the impact of air masses far away from the fire sources. Below are some illustrations of these satellite maps over the last 10 days.

Natural-color images from MODIS-Aqua sensor, over east Canada within the period of 2017.07.31-2017.08.08. Red points indicate actively burning areas identified from MODIS, on-board Terra and Aqua platforms. Smokes stretch very far away from these points (Source: https://worldview.earthdata.nasa.gov).

Aerosol particles, suspended in air, monitored via MODIS-Aqua sensor, over east Canada within the period of 2017.07.31-2017.08.08. Here, the Aerosol Optical Depth (AOD) is plotted, a proxy of aerosol load or amount. Values are in the range of 0.5 (yellow-orange) – 2 (dark red – large amount of particles) (Source: https://worldview.earthdata.nasa.gov).

The integrated amounts of aerosol particles that are suspended in the atmosphere can be quantified, and their horizontal distribution monitored. This is an important input for air quality models in charge of predicting the air quality for populations.

Some satellite sensors can distinguish some aerosol – particle – types. Here, the so-called UVAI index derived from the OMI-Aura sensor, over Canada within the period of 2017.07.31-2017.08.08, indicate in orange-red a large presence of very dark (i.e. absorbing) particles (UVAI values in the range of 2-5) (Source: https://worldview.earthdata.nasa.gov).

Knowing the type of these particles (i.e. whether they are dark or brighter) is of great importance for scientists and researchers. This directly gives insights on how these aerosols affect our atmosphere radiation, and consequently our climate on the long-term. Satellite sensors measuring light in the UV such as the Dutch-Finnish OMI mission, on-board the NASA Aura platform, provides with an important index (here named UV Absorbing Index or UVAI) to identify absorbing (i.e. very dark) aerosol particles on a daily-global coverage.

Finally, wildfires do not only release smoke and particles, which already pose a problem for human respiratory health, but also a mix of toxic gases. One of the most important is CO – Carbon monoxide. Infrared sensors such as the European IASI mission, on-board Metop-A and B, quantify everyday the amount of CO present in the atmosphere. On some specific days in August, concentration values were comparable to those associated with African and South-American fires.

This post was written by Julien Chimot and my colleague Jonathan Izett. Find more information on Jonathan via his Linkedin profile, and his website on his research work focused on the formation, evolution and prediction of fog in the atmospheric boundary layer.